Abstract
Wealthy adults tend to live longer than those with less wealth. However, a challenge in this area of research has been the reduction of potential confounding by factors associated with the early environment and heritable traits, which could simultaneously affect socioeconomic circumstances in adulthood and health across the life course. To identify the association between net worth at midlife and subsequent all-cause mortality in individuals as well as within siblings and twin pairs. This cohort study conducted a series of analyses using data from the Midlife in the United States (MIDUS) study, an ongoing national study of health and aging. The sample included adults (unrelated individuals, full siblings, and dizygotic and monozygotic twins) aged 20 to 75 years, who participated in wave 1 of the MIDUS study, which occurred from 1994 to 1996. The analyses were conducted between November 16, 2019, and May 18, 2021. Self-reported net worth (total financial assets minus liabilities) at midlife (the middle years of life). All-cause mortality was tracked over nearly 24 years of follow-up, with a censor date of October 31, 2018. Survival models tested the association between net worth and all-cause mortality. Discordant sibling and twin analyses compared longevity within siblings and twin pairs who, given their shared early experiences and genetic backgrounds, were matched on these factors. The full sample comprised 5414 participants, who had a mean (SD) age of 46.7 (12.7) years and included 2766 women (51.1%). Higher net worth was associated with lower mortality risk (hazard ratio [HR], 0.95; 95% CI, 0.94-0.97; P < .001). Among siblings and twin pairs specifically (n = 2490), a similar within-family association was observed between higher net worth and lower mortality (HR, 0.94; 95% CI, 0.91-0.97; P = .001), suggesting that the sibling or twin with more wealth tended to live longer than their co-sibling or co-twin with less wealth. When separate estimates were performed for the subsamples of siblings (HR, 0.94; 95% CI, 0.90-0.97; P = .002), dizygotic twins (HR, 0.94; 95% CI, 0.86-1.02; P = .19), and monozygotic twins (HR, 0.95; 95% CI, 0.87-1.04; P = .34), the within-family estimates of the net worth-mortality association were similar, although the precision of estimates was reduced among twins. This cohort study found that wealth accumulation at midlife was associated with longevity in US adults. Discordant sibling analyses suggested that this association is unlikely to be simply an artifact of early experiences or heritable characteristics shared by families.
Highlights
Socioeconomic disparities in life expectancy are substantial in size.[1,2,3] Financial wealth or net worth, which is the value of an individual’s assets minus liabilities,[4,5] is directly associated with longevity[4,6,7,8,9] and, in some studies, has been found to be more strongly associated with mortality than other indicators of socioeconomic status, such as occupational prestige, educational attainment,[7] and income.[6]
Higher net worth was associated with lower mortality risk
Among siblings and twin pairs (n = 2490), a similar within-family association was observed between higher net worth and lower mortality (HR, 0.94; 95% CI, 0.91-0.97; P = .001), suggesting that the sibling or twin with more wealth tended to live longer than their co-sibling or co-twin with less wealth
Summary
Socioeconomic disparities in life expectancy are substantial in size.[1,2,3] Financial wealth or net worth, which is the value of an individual’s assets (such as savings, real estate, and vehicles) minus liabilities,[4,5] is directly associated with longevity[4,6,7,8,9] and, in some studies, has been found to be more strongly associated with mortality than other indicators of socioeconomic status, such as occupational prestige, educational attainment,[7] and income.[6]. In sibling-comparison studies, factors that are shared between siblings are controlled.[11,12] Twin comparisons provide an even greater control of family-level early-life confounding and, in the case of monozygotic (MZ) twins, control for all heritable genetic factors.[13,14] Previous research found that discordance in occupational prestige was associated with cardiovascular risk[15] and overall mortality[16]; twins with lower-prestige jobs had worse health on both outcomes compared with their co-twins with higher-prestige jobs This pattern suggests that socioeconomic disparities in health are affected by experiential factors in adulthood over and above any potential confounders that involve the siblings’ shared early environment and genetic characteristics. In other discordant sibling and twin analyses, educational attainment[16,17,18,19,20,21,22] and composite measures of adult socioeconomic position[23] have been associated with better adult health outcomes[18,22,23] and longevity.[16,17,19,20,21] results from these and other studies that used different methods do suggest these associations may be partially explained by shared familylevel environmental factors[17,18,19,21,22] or genetic predispositions.[10,18,23]
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